Pizzas and other fast food products are generally cooked in ovens to bake the crust and to bake, heat, and melt the toppings. One style of pizza oven is a deck oven that uses radiant and conductive heat for cooking. Typically, the required baking time in a deck oven would be in a range between about 15 and 25 minutes.
An impingement oven uses mostly convection to heat the pizza, as well as some heat of conduction. The newer pizza ovens typically are impingement ovens which move the pizzas through the oven on conveyors while others are equipped with rotating turntables for moving the pizza relative to air streams that impinge the pizza.
An impingement oven is described in U.S. Pat. No. 4,679,542 to Don Paul Smith. These ovens, which are a special type of forced convection oven using columnated heated air to impact the pizza, have increased heat transfer capabilities and therefore have reduced the bake time of pizza and other foods significantly.
Impingement ovens have achieved wide acceptance among pizza restaurants, and pizza delivery systems, especially those which deal with high volume and fast service. The typical bake time for the commercially available impingement ovens is in the range of about 5 to 9 minutes. However, by using partially pre-baked crust in an impingement oven at a relatively high temperature, the final cooking time may be reduced to a little over one minute.
U.S. Pat. No. 4,965,435 discloses a jet impingement oven in which spent air from jets formed by tubes is drawn toward the front wall of the oven. U.S. Pat. No. 5,310,978 discloses an oven in which spent is drawn toward opposite sides of the oven for returning the spent air to a fan. U.S. Pat. No. 5,510,601 discloses an air impingement oven wherein air is delivered by a fan into hollow fingers for forming columns of heated air that are projected through tubes. After the columns of air impinge against the surface of the food product, the spent air is drawn toward the back wall of the oven.
Pellicane U.S. Pat. No. 4,960,100 discloses a plurality of spaced discrete nozzles, each nozzle defining a slot orifice disposed transverse to the path of travel of a conveyor. The nozzles are spaced along the path of travel so that the surface of the product to be cooked which is impinged upon by air flowing through the nozzles will pass from an area of high velocity to an area of low velocity between the slot orifices.
Moshonas U.S. Pat. No. 5,671,660 discloses a blower which draws air from a baking chamber through apertures into a suction chamber extending between air distributors which dispense air back into the baking chamber.
In each of the patents referred to above, after the jets impinge upon the surface of the product, the spent air is drawn around or through jets of air that have not yet impinged against the surface of the product. This tends to disrupt or "wash out" the collimated jets of air.